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Weekly space gallery for January 28, 2014

WELCOME TO OUR WEEKLY COLLECTION of the best astronomy and space exploration images taken by observatories around the world and in space. Each week we’ll bring you a selection of our favourite recent images – if you like them (and we hope you do), please share them with your friends. And don’t forget you can elect to have this and other stories emailed direct to your inbox, just by signing up to our free email service – see the Subscribe box in the column at right.

So, let’s get started on this week’s images.

1. Disruptive black hole

A black hole lives at the heart of the white galaxy in the middle of this image. Extensive clouds of hot gas, detected by NASA’s Chandra X-ray Observatory satellite and coloured purple, should be the raw material from which countless new stars would be born. But jets of energy emanating from the vicinity of the black hole have disrupted the gas, forming two cavities on either side of the centre and sending out shock waves that prevent the gas from clumping and forming stars. The galaxy in question is called RX J1532+3201, and it is 3.9 billion light years from Earth. Image credit: X-ray: NASA / CXC / Stanford / J.Hlavacek-Larrondo et al, Optical: NASA / ESA / STScI / M.Postman & CLASH team.

Gas surrounding galaxy RX J1532+3201

Hot gas surrounds galaxy RX J1532+3201.

 

2. Titan, top and bottom

This black and white image of Titan, Saturn’s largest moon, was taken through a special infrared filter to bring out detail in its atmosphere. Visible at the far north (top) is a haze that stands up above the bulk of atmosphere, while near the south pole is the South Polar Vortex – thought to be an uplifted mass of air caused by a change in the seasons. This image was taken by NASA’s Cassini spacecraft from a distance of 2.5 million kilometres. Cassini has been orbiting Saturn since 2004. Courtesy NASA / JPL-Caltech / Space Science Institute.

Titan

Haze is visible in Titan’s north, while a polar vortex is in the south.

 

3. Brown dwarf revealed

Astronomers have used special techniques to block out the light of a star (leaving a speckled appearance) to reveal a dim brown dwarf that is in orbit around it. Brown dwarfs are bodies at are two big to be planets, but two small to be proper stars. They give off a relatively small amount of heat. The astronomers are particularly interested in studying the brown dwarf’s atmosphere, by analysing the light that reflects from it. “This object is old and cold and will ultimately garner much attention as one of the most well-studied and scrutinised brown dwarfs detected to date,” says Justin R. Crepp of the University of Notre Dame. “With continued follow-up observations, we can use it as a laboratory to test theoretical atmospheric models. Eventually we want to directly image and acquire the spectrum of Earth-like planets. Then, from the spectrum, we should be able to tell what the planet is made out of, what its mass is, radius, age, etc., basically all relevant physical properties.” Courtesy Crepp et al. 2014, ApJ.

Brown dwarf image

By blocking most of the light of its parent star, a faint brown dwarf is revealed.

 

4. A gallery of galaxies

The Hubble Space Telescope was used to make this long-exposure image of the galaxy cluster Abell 2744, which comprises the bright galaxies in the foreground. Fainter background galaxies appear to have become distorted as their light is bent by Abell 2744’s gravity. Astronomers have counted up to 3,000 of these background galaxies in the full-size version of this image alone. Courtesy NASA / ESA.

Galaxy cluster Abell 2744

A long Hubble exposure of galaxy cluster Abell 2744 also reveals other galaxies in the far background.

 

5. We have lift-off

NASA’s newest Tracking and Data Relay System Satellite (TDRSS) was launched on January 23 from the Kennedy Space Centre in Florida. There are several TDRSS satellites circling Earth, through which NASA can communicate with spacecraft in Earth orbit. They are not directly involved in communicating with deep space missions. Courtesy NASA / Tony Grey.

Time exposure of TDRSS launch

Lift off of NASA’s latest TDRSS satellite.

 

6. A supernova surprise

A supernova was spotted in galaxy M82 on January 21, causing great excitement amongst astronomers. M82 is only 12 million light years from Earth, making the supernova (called SN 2014J) one of the closest in many years. Many observatories broke into their normal scheduled operations to make observations of the supernova, including NASA’s Swift orbiting observatory. This picture, sensitive to ultraviolet light, shows the supernova standing out brightly against the amorphous background of the rest of M82. Courtesy NASA / Swift / P. Brown, TAMU.

Swift image of galaxy M82 and its supernova

A Swift image of galaxy M82 and its supernova.

Story by Jonathan Nally.

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GALLERY: Black holes galore

AN ASSORTMENT OF BLACK HOLES lights up a new image from NASA’s Nuclear Spectroscopic Telescope Array, or NuSTAR. Although the coloured blobs might not look like much, every one of them is a black hole located inside the hearts of a galaxy.

The different colours represent different energies of X-ray light. The red, yellow and green colours represent black holes seen previously by NASA’s Chandra X-ray Observatory (with red denoting the lowest-energy X-ray light). The colour blue shows black holes recently detected by NuSTAR, which is uniquely designed to detect the highest-energy X-ray light.

Image showing X-ray emission from black holes

Every one of the blobs you can see here, represents the location of a black hole. Although black holes cannot be directly seen, the X-ray light given off by hot gas in the vicinity can – and that’s what we see here; X-ray emission detected by the Chandra and NuSTAR space observatories.

The black holes in this picture are between about 3 to 10 billion light-years away.

The X-rays aren’t coming from the black holes themselves, since nothing can escape the gravitational grip of a black hole. Rather, they are coming from hot gas in the vicinity of the black holes.

Why do some black holes produce more high-energy X-ray light than others? Astronomers say this is because the black holes are more actively feeding off surrounding clouds of dust and gas – a process which heats up the gas and makes it emit X-rays.

The image shows an area, called the COSMOS field, that has been studied in great detail by many telescopes (COSMOS stands for Cosmic Evolution Survey). Red and green represent X-ray light seen by Chandra. Blue is for the kind of X-ray light that can only be seen by NuSTAR.

Adapted from information issued by NASA / JPL-Caltech / Yale University.

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Gallery: The ‘Fireworks Galaxy’

NGC 6946 IS A MEDIUM-SIZED, face-on spiral galaxy located about 22 million light years away from Earth. In the past century, eight supernovae have been observed to explode in the arms of this galaxy. Chandra space telescope observations (coloured purple in this iamge) have, in fact, revealed three of the oldest supernovae ever detected at X-ray wavelengths, giving more credence to its nickname of the ‘Fireworks Galaxy.’ This composite image also includes optical data from the ground-based Gemini Observatory.

NGC 6949

NGC 6949, also known as the ‘Fireworks Galaxy’. Image credit: X-ray: NASA / CXC / MSSL / R.Soria et al, Optical: AURA / Gemini Obs

More information and downloadable wallpaper images: nasa.gov/mission_pages/chandra/multimedia/fireworks-galaxy-ngc6946.html

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Video: Mystery X-ray source in distant galaxy

SINCE THE 1980s, astronomers have known about a mysterious class of objects that they call “ultraluminous X-ray sources,” or ULXs. They named them this because these objects give off more X-rays than most other binary star systems where black holes or neutron stars are in orbit around a normal companion star.

Recently, scientists using NASA’s Chandra X-ray Observatory and optical telescopes spotted a ULX in the spiral galaxy M83 that was acting even more strangely. This ULX increased its output in X-rays by 3,000 times over the course of several years.

Using clues found in the X-ray and optical data, researchers think this ULX may be a member of a population of black holes that up until now was suspected to exist but had not been confirmed.

These black holes, which are the smaller stellar-mass black holes (ones that form from the collapse of a giant star), are older and more active than previously thought.

Video courtesy NASA / CXC. Image close-ups – X-ray, NASA / CXC / Curtin University / R. Soria et al.; optical, NASA / STScI / Middlebury College / F. Winkler et al.

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Inside-out exploding star

Cassiopeia A: artist's impression of the precursor star and real X-ray image of the remnant

Before and after the explosion. Colour coded elements in artist's impression of the star's core match up with real observations of Cassiopeia A. Iron, shown in blue, has somehow gone from being in the middle of the star to the outskirts of the supernova remnant.

IN THE NORTHERN CONSTELLATION Cassiopeia lies a famous supernova remnant, a gas cloud that represents the shattered remains of a once-titanic star.

Known as Cassiopeia A, it is hard to see at normal visible light wavelengths but shines strongly at radio and X-ray wavelengths.

A supernova of this kind occurs when a massive star runs out of nuclear fuel and can no longer produce energy. Without an outflow of energy to keep the star “inflated”, it’s huge mass crushes inwards … producing an implosion followed by an explosion that tears the star apart.

In the millions of years leading up to the explosion, the star’s innards become layered with different elements as a result of different nuclear fusion processes. In the core there is a globe of iron. Surrounding that are layers of sulphur, silicon, magnesium, neon and oxygen.

It would seem to make sense that when the star explodes, the outer layers would end up on the outskirts of the resulting gas cloud, with the iron concentrated toward the middle.

But by compiling a staggering one million seconds worth of X-ray observations by satellite telescopes, astronomers have found that this is not the case for Cassiopeia A.

The observations show that the distribution of sulphur, silicon, magnesium and neon is about as expected. But the iron is spread around the outer part of the supernova remnant, and there’s none in the middle.

The astronomers think there must have been some sort of “instability” in the supernova explosion process, which turned the star inside out.

Story by Jonathan Nally. Images courtesy (illustration) NASA / CXC / M.Weiss; (X-ray) NASA / CXC / GSFC / U.Hwang & J.Laming.

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Ancient supernova seen in a new light

RCW 86

This is all that remains of a supernova explosion that was seen by Chinese astronomers in the year 185 CE. The remnant gas cloud is called RCW 86, and is approximately 8,000 light-years from Earth.

A TWISTED AND TANGLED GAS CLOUD is all that remains of the oldest documented example of a supernova, called RCW 86.

Chinese stargazers witnessed the event in 185 CE, documenting a mysterious ‘guest star’ that remained in the sky for eight months.

The image combines data from four different space telescopes to create a multi-wavelength view.

X-ray images from the European Space Agency’s XMM-Newton Observatory and NASA’s Chandra X-ray Observatory are combined to form the blue and green colours in the image. The X-rays show the interstellar gas that has been heated to millions of degrees by the passage of the shock wave from the supernova.

Infrared data from NASA’s Spitzer Space Telescope, as well as NASA’s Wide-Field Infrared Survey Explorer (WISE) are shown in yellow and red, and reveal dust radiating at a temperature of several hundred degrees below zero, warm by comparison to normal dust in our Milky Way galaxy.

By studying the X-ray and infrared data together, astronomers were able to determine that the cause of the explosion witnessed nearly 2,000 years ago was a Type Ia supernova, in which an otherwise-stable white dwarf, or dead star, was pushed beyond the brink of stability when a companion star dumped material onto it.

Furthermore, scientists used the data to solve another mystery surrounding the remnant—how it got to be so big in such a short amount of time.

By blowing out a ‘wind’ prior to exploding, the white dwarf was able to clear out a huge ‘cavity,’ a region of very low-density surrounding the system. The explosion was able to expand into this cavity much faster than it otherwise would have.

RCW 86 is approximately 8,000 light-years away.

Adapted from information issued by NASA / JPL-Caltech / B. Williams (NCSU).

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Take a tour of the Crab Nebula

THE CRAB NEBULA IS ONE OF THE BRIGHTEST sources of high-energy radiation in the sky. Little wonder—it’s the expanding remains of an exploded star, a supernova seen in 1054.

Scientists have used virtually every telescope at their disposal, including NASA’s Chandra X-ray Observatory, to study the Crab.

The supernova left behind a magnetised neutron star—a pulsar. It’s about the size of Washington DC, but it spins 30 times per second. Each rotation sweeps a lighthouse-like beam past us, creating a pulse of electromagnetic energy detectable across the spectrum.

The pulsar in the Crab Nebula is among the brightest sources of high-energy gamma rays. Recently, NASA’s Fermi Gamma Ray Observatory and Italy’s AGILE Satellite detected strong gamma-ray flares from the Crab, including a series of “superflares” in April 2011.

To help pinpoint the location of these flares, astronomers enlisted Chandra space telescope.

With its keen X-ray eyes, Chandra saw lots of activity, but none of it seems correlated with the superflare. This hints that whatever is causing the flares is happening with about a third of a light-year from the pulsar. And rapid changes in the rise and fall of gamma rays imply that the emission region is very small, comparable in size to our Solar System.

The Chandra observations will likely help scientists to home in on an explanation of the gamma-ray flares one day.

Even after a thousand years, the heart of this shattered star still offers scientists glimpses of staggering energies and cutting edge science.

Adapted from information issued by Harvard-Smithsonian Centre for Astrophysics. Still image courtesy (X-ray) NASA / CXC / SAO / F.Seward, (optical) NASA / ESA / ASU / J.Hester & A.Loll, (infrared) NASA / JPL-Caltech / Univ. Minn. / R.Gehrz.

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Black holes born soon after Big Bang

Illustration of supermassive black hole

Astronomers have found the first direct evidence that black holes existed when the Universe was less than a tenth of its present age. (Artist's impression)

USING THE MOST SENSITIVE X-ray image ever taken, University of Hawaii astronomer Ezequiel Treister and colleagues have found the first direct evidence that black holes existed when the Universe was less than a tenth of its present age.

Between 30 and 100 percent of the 200 distant galaxies they observed contained a central black hole that was voraciously consuming the gas and stars that surrounded them.

This discovery was made with NASA’s orbiting Chandra X-ray Observatory.

“Black holes are objects whose gravity is so strong that not even light can escape from them. Until now, we had no idea what the black holes in these early galaxies were doing—or if they even existed,” said Treister, lead author of the study that appears in this week’s Nature. “Now we know they are there and they are growing like gangbusters.”

“It appears we’ve found a whole new population of baby black holes,” said co-author Kevin Schawinski of Yale University. “We think these babies will grow by a factor of about a hundred or a thousand, eventually becoming like the giant black holes we see today almost 13 billion years later.”

A population of very young black holes in the early Universe had been predicted, but not yet observed. Detailed calculations show that the total amount of black hole growth observed by this team is about a hundred times higher than recent estimates.

Because these very young black holes are nearly all enshrouded in thick clouds of gas and dust, optical telescopes frequently cannot detect them. However, the high energies of X-ray light can penetrate these veils, allowing the black holes inside to be studied.

Adapted from information issued by the University of Hawaii.

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The Case of the Cosmic Crab

A NEW MOVIE FROM NASA’S Chandra X-ray Observatory shows a sequence of images of the Crab Nebula, taken over an interval of seven months and showing dramatic variations.

The Crab Nebula is one of the most famous objects in the sky. It is the remnant cloud from a supernova (exploding star) that was seen by astronomers in China and other countries in the year 1054.

At the centre of the nebula is a pulsar, a rapidly spinning neutron star. It has a mass greater than our Sun but is only tens of kilometres wide, and is spinning at the rate of 30 times per second.

The pulsar’s spin is gradually slowing down, and as it does so large amounts of energy are injected into its surroundings. In particular, a high-speed wind of matter and anti-matter particles ploughs into the surrounding nebula, creating a shock wave that forms the expanding ‘ring’ seen in the movie.

In addition, ‘jets’ shooting out from the poles of the pulsar spew X-ray emitting matter and antimatter particles in a direction at right angles to the ring.

The goal of the latest Chandra observations was to pinpoint the location of remarkable flares spotted by NASA’s Fermi Gamma Ray Observatory satellite and Italy’s AGILE satellite.

A strong gamma-ray flare was detected from the Crab in September 2010, followed by an even stronger series of “superflares” in April 2011. The gamma-ray satellites were not able to locate the source of the flares within the nebula, but it was hoped that Chandra, with its high-resolution images, would.

Scientists have put together a short sequence of the images taken by Chandra, showing the remarkable changes in the nebula:

Chandra began observing the Crab on monthly intervals beginning six days after the discovery of the gamma-ray flare in September 2010. This established a baseline of seven images before the superflare was seen last month.

What was unexpected, though, was that nothing significant showed up in the Chandra observations as compared with the Fermi observations. Astronomers are now trying to figure out why that is so.

One possible explanation is that the gamma-ray flares picked up by Fermi happened very close to the pulsar, in which case they would have been missed by Chandra, because the Crab pulsar is so bright that the detectors are in essence “overexposed” so variations from that region cannot be observed. (Note that in the movie an artificial source of constant brightness is included to show the position of the pulsar.)

Adapted from information issued by CXC. Crab Nebula image courtesy (X-ray) NASA / CXC / SAO / F. Seward; (optical) NASA / ESA / ASU / J. Hester & A. Loll; (infrared) NASA / JPL-Caltech / Univ. Minn. / R. Gehrz.

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Black hole in the ‘Eye of Sauron’

Eye of Sauron image of NGC 4151

This false-colour image (using X-ray, visible light and radio wave data) of the core of galaxy NGC 4151 resembles the Eye of Sauron from the Lord of the Rings movies. In reality, it shows the region surrounding a supermassive black hole.

  • Spiral galaxy NGC 4151 has a growing, giant black hole at its centre.
  • Dubbed “The Eye of Sauron” for its resemblance to the “The Lord of the Rings” character

AT THE HEART OF MANY (perhaps most) galaxies there lives a dark, malevolent force—a black hole.

And they aren’t just ordinary black holes. They are giants…what astronomers call ‘supermassive’ black holes, which can have masses hundreds of millions or billions of times the mass of our Sun.

One such galaxy is NGC 4151. Located about 43 million light-years from Earth, it is one of the nearest galaxies to contain an actively growing black hole.

A new false-colour image put together using different wavelength data makes the local region surrounding the black hole look like the ‘Eye of Sauron’ from the Lord of the Rings movies.

In the ‘pupil’ of the eye, X-rays (coloured blue) detected by the Chandra X-ray Observatory are combined with visible light wavelengths (yellow) showing positively charged hydrogen atoms (from observations with the Jacobus Kapteyn Telescope in the Canary Islands).

The red surrounding the pupil shows neutral hydrogen detected by radio observations with the Very Large Array radio telescope in the USA.

Because it is so close (in astronomical terms), NGC 4151 offers one of the best opportunities to study the interaction between an active supermassive black hole and the surrounding gas of its host galaxy.

Such interaction, or ‘feedback’, is recognised to play a key role in the growth of both black holes and their host galaxies.

Gas falls into the black hole, feeding it and making it grow larger.

But as the gas approaches the black hole, it heats up…to the point where some of it shoots back into the galaxy in a process known as an outflow. That hot gas emits X-rays.

If the X-ray emission seen in the core of NGC 4151 indeed originates from hot gas heated by the outflow from the black hole, it would be strong evidence for black hole feedback occurring within individual galaxies.

Such feedback has already been seen on larger scales—in clusters of galaxies such as the Perseus Cluster, where active black holes interact with surrounding gas.

Adapted from information issued by Chandra X-ray Centre. Image credit: X-ray, NASA / CXC / CfA / J.Wang et al.; optical, Isaac Newton Group of Telescopes, La Palma / Jacobus Kapteyn Telescope; radio, NSF / NRAO / VLA.

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